I would like to find comparisons between YUV and D-Terminal on Game Cube thanks to my friend google, but there is absolutely nothing... Are the pictures similar ? Or is the D-Terminal picture slightly better ? And given that only people living in Japan can give me this answer, they are pretty rare. What is interesting is that the D-Terminal cable seems to force the progressive scan on some Pal Games when a Pal Game Cube with a Pal game is hooked up to a TV with a D-Terminal cable.
A D-Terminal is just a component port all in one. Most Japanese TVs have no component ports because they have the D-Terminal ports on them. I can't say for Game Cube but for other systems the D-terminal provides a wonderful picture from 480i all the way up o 1080p depending on the level accepted by your TV. Yakumo
Some d-terminal (and Japanese RGB) cables can be costly in the west. Ready made adapters to component appear easy to find online here, yet NOT cheap.
Most D-terminal cables only support up to D4 (720p). D5 is defined as 1080p but I've never seen any device which supports it. Like what the above posters said, it's the same as component.